/**
 * @widoc $.generateGuid
 * @namespace aux
 * @des 生成唯一键 guid
 * @type function
 * @param {object} key guid 的前缀
 * @return {string} str 返回生成的字符串
 */
$.generateGuid = function(key){
    var guid = 'xxxxxxxx-xxxx-4xxx-yxxx-xxxxxxxxxxxx'.replace(/[xy]/g, function(c){
        var r = Math.random() * 16 | 0, v = c == 'x' ? r : (r & 0x3 | 0x8);
        return v.toString(16);
    });
    return (key || '') + guid;
};